For the most part, 'cross bars are the same as road bars. You want to measure them the same; that is, measure your shoulder width (from bone to bone... or your suit jacket size) and use that. If it's a 42, go for a 42cm bar.
Some riders opt for something slightly wider for more stability, like a 44cm, but it comes down to personal preference.
Not knowing what components you have on your Crossroads, your brake/ shift options are either brifters (brake/shift combo) or standard road levers with bar end shifters. You can also add those 'cross brake levers on the tops of the bars for when you ride in that position. Bank on replacing all of the cables no matter which route you go.
Are you going to use the bike in a true cyclocross application, or just for road/ multi use trail riding? Where you ride will also determine shifter/ brake lever choices.
Alan
